Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752550Ab0HLF0r (ORCPT ); Thu, 12 Aug 2010 01:26:47 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:39218 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750919Ab0HLF0p (ORCPT ); Thu, 12 Aug 2010 01:26:45 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=from:to:subject:references:cc:date:message-id:mime-version :content-type; b=w1BadbosDSEAWZ7rZs+QQjMVY7qN/QWGADk9o6vmet5VsC4MmVfRKfrBJ9g1va2j7X lR1imAR94T0dT70D1gNG2MB2EK2dzcqKYU2l/0Yylgnhl8G+H4H8OwhDssKA9m9qvGW7 KLGeRTz8oHIQAwyf9cVO1DPtm14jkpxWXibfs= From: "Patrick J. LoPresti" To: linux-nfs@vger.kernel.org Subject: [PATCH] nfs: lookupcache coherence bugs in WCC update path (revised) References: <87lj8ckb1e.fsf@patl.com> CC: linux-kernel@vger.kernel.org Date: Wed, 11 Aug 2010 22:26:36 -0700 Message-ID: <8762zgmmer.fsf@patl.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2922 Lines: 68 (Well, crud. I screwed up the previous diff and was missing a close-curly. This version actually compiles...) This patch fixes some coherence bugs in the NFS "dentry lookup cache". The NFS dentry lookup cache provides the nfs_force_lookup_revalidate() call to invalidate all cached dentries associated with an inode. In general, the NFS client uses the ctime and mtime in the inode to detect when changes are made on the server. Therefore, to maintain cache coherence, nfs_force_lookup_revalidate() must be called whenever the ctime or mtime of a directory inode is updated with fresh data from the server. There are a few spots in nfs_wcc_update_inode() where this rule is violated, making it possible for the lookup cache to return arbitrarily stale data. This actually bit me in practice. I have an application where a negative dentry results in -ENOENT for a file that was created 30+ minutes earlier (despite the "noac" mount option). Unfortunately I cannot share my test case, but I believe the following simple patch is "obviously correct", and I can confirm that it fixes my issue. CC: stable Signed-off-by: Patrick LoPresti --- --- linux-2.6.35/fs/nfs/inode.c.orig 2010-08-01 15:11:14.000000000 -0700 +++ linux-2.6.35/fs/nfs/inode.c 2010-08-11 22:18:30.000000000 -0700 @@ -819,21 +819,29 @@ static void nfs_wcc_update_inode(struct && (fattr->valid & NFS_ATTR_FATTR_CHANGE) && nfsi->change_attr == fattr->pre_change_attr) { nfsi->change_attr = fattr->change_attr; - if (S_ISDIR(inode->i_mode)) + if (S_ISDIR(inode->i_mode)) { nfsi->cache_validity |= NFS_INO_INVALID_DATA; + nfs_force_lookup_revalidate(inode); + } } /* If we have atomic WCC data, we may update some attributes */ if ((fattr->valid & NFS_ATTR_FATTR_PRECTIME) && (fattr->valid & NFS_ATTR_FATTR_CTIME) - && timespec_equal(&inode->i_ctime, &fattr->pre_ctime)) - memcpy(&inode->i_ctime, &fattr->ctime, sizeof(inode->i_ctime)); + && timespec_equal(&inode->i_ctime, + &fattr->pre_ctime)) { + if (S_ISDIR(inode->i_mode)) + nfs_force_lookup_revalidate(inode); + memcpy(&inode->i_ctime, &fattr->ctime, sizeof(inode->i_ctime)); + } if ((fattr->valid & NFS_ATTR_FATTR_PREMTIME) && (fattr->valid & NFS_ATTR_FATTR_MTIME) && timespec_equal(&inode->i_mtime, &fattr->pre_mtime)) { memcpy(&inode->i_mtime, &fattr->mtime, sizeof(inode->i_mtime)); - if (S_ISDIR(inode->i_mode)) + if (S_ISDIR(inode->i_mode)) { nfsi->cache_validity |= NFS_INO_INVALID_DATA; + nfs_force_lookup_revalidate(inode); + } } if ((fattr->valid & NFS_ATTR_FATTR_PRESIZE) && (fattr->valid & NFS_ATTR_FATTR_SIZE) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/